Various urethane resin compositions have been widely used as sealing agents, adhesive agents, and the like.
As such urethane resin compositions, two-part type compositions containing a polyol compound and an isocyanate compound, and one-part type compositions that are curable by moisture in the air or the like have been known. However, from the perspective of ease in handling that does not require mixing/adjusting the composition on site when the composition is used, or the like, use of one-part moisture-curable polyurethane compositions has been increasing recently.
For example, Japanese Unexamined Patent Application No. 2004-168957A describes “a one-part moisture-curable polyurethane composition comprising: an isocyanate silane compound, the isocyanate silane compound being a reaction product of a compound, which has at least three isocyanate groups and which is obtained by reacting trimethylolpropane with diisocyanate compound, with a secondary aminosilane having a specific structure; and a urethane prepolymer”.
Furthermore, Japanese Unexamined Patent Application Nos. 2006-131794A and 2006-131802A describe a one-part moisture-curable urethane composition comprising, relative to a composition prepared in advance containing a predetermined urethane prepolymer, filler, and plasticizer: “a compound (A) obtained by reacting a compound, obtained by reacting trimethylolpropane with bifunctional isocyanate in a manner that the equivalent weight proportion of NCO groups relative to OH groups is from 0.8 to 1.5, with a compound, having an imino group in which an aryl group is directly bonded to a nitrogen atom and having a hydrolyzable silyl group, in a manner that the equivalent weight proportion of NCO groups relative to NH groups is from 1.8 to 3.5”; “a compound (B) obtained by reacting a compound that is at least one type selected from the group consisting of isocyanurates and biurets of bifunctional isocyanate and compounds obtained by reacting bifunctional isocyanate with triol, with a compound, having an imino group in which an aryl group is directly bonded to a nitrogen atom and having a hydrolyzable silyl group, in a manner that the equivalent weight proportion of NCO groups relative to NH groups is from 1.8 to 3.5”; and “a compound (C) that is at least one type selected from the group consisting of isocyanurates and biurets of bifunctional isocyanate and compounds obtained by reacting bifunctional isocyanate with triol”.
Furthermore, Japanese Unexamined Patent Application No. 2008-038019A describes “a one-part moisture-curable urethane resin composition comprising: a urethane prepolymer (A); a compound (B) obtained by reacting at least one type of modified hexamethylene diisocyanate selected from the group consisting of reaction products of hexamethylene diisocyanate and trimethylolpropane, biurets of hexamethylene diisocyanate, and isocyanurates of hexamethylene diisocyanate, with an imino group-containing alkoxysilane; a polymer (C) having a particular structural unit; and a catalyst (D).
However, it was found that, depending on the types or contents of compounds other than the urethane prepolymer and the filler (e.g. isocyanate silane compound in Japanese Unexamined Patent Application No. 2004-168957A, or the like), at least one physical property among shear modulus, adhesion under high-temperature high-humidity environments, or storage stability may be deteriorated with conventionally known one-part moisture-curable polyurethane compositions described in Japanese Unexamined Patent Application Nos. 2004-168957A, 2006-131794A, 2006-131802A and 2008-038019A, or the like.